1. Field of the Invention
The subject invention generally pertains to a vehicle restraint that engages a truck""s rear ICC bar to help prevent the truck from accidentally pulling away from a loading dock and more specifically to a vehicle restraint that responds to vertical movements of the truck, as the truck is being loaded or unloaded of its freight.
2. Description of Related Art
When loading or unloading a truck parked at a loading dock, it is generally a safe practice to help restrain the truck from accidentally moving too far away from the dock. This is often accomplished by a hook-style vehicle restraint that engages what is often referred to in the industry as an ICC bar or a Rear Impact Guard (RIG). An ICC bar or RIG is a bar or beam that extends horizontally across the rear of a truck, below the truck bed. Its primary purpose is to help prevent an automobile from under-riding the truck in a rear-end collision. However, an ICC bar also provides a convenient structure for a hook-style restraint to reach up in front of the bar to obstruct the bar""s movement away from the dock. To release the truck, many restraints lower to a stored position below the bar, which then allows the next truck to back into the dock. Other hook-style restraints store in a normally raised position and include an inclined lead-in that an ICC bar uses to help push the restraint underneath the bar as the truck backs into the dock, as disclosed in U. S. Pat. Nos. 5,702,223; 4,443,150; and 4,938,647. Once underneath the bar, usually a barrier rises in front of the bar (e.g., rotates to such a position) to restrain the truck.
Current hook-style vehicle restraints provide a wide variety of advantages and features. Some restraints have a sensor or switch intended for determining whether the hook or barrier is properly positioned to obstruct the ICC bar, as disclosed in U.S. Pat. No. 4,759,678. However, in the ""678 device, an ICC bar catching the very distal end of the restraint carriage (i.e., just in front of the hook) would appear to allow the hook to rise and trip the switch to indicate that the ICC bar was restrained, when actually the bar would be in front of the hook. This problem is avoided by the restraints of U. S. Pat. Nos. 4,488,325 and 5,297,921, which include switches that more directly sense the position of an ICC bar. However, these restraints, as well as the ""678 restraint, have a significantly high vertical profile in their lowered, stored positions. The high profile may prevent some especially low ICC bars from passing over the top of the restraint, even when the restraint is lowered to its stored position.
Further, to move a restraint barrier or hook, often a complicated linkage (for various reasons) is employed to raise or lower the barrier under the power of an actuator, as disclosed in U. S. Pat. Nos. 4,861,217; 4,674,941; and 4,830,563. Although the linkages may provide some benefit, their relative complexity can add to their maintenance and cost.
It is usually desirable for a restraint to allow for some vertical movement of the ICC bar, which is often caused by weight being added or removed from the truck (and thus the suspension) while at the loading dock. The changes in weight can be due to cargo being added or removed, and/or can be due to a forklift driving on and off the truck bed. For truck beds with rear air suspension, an ICC bar may move up and down several inches. If the barrier does not rise with the bar, the bar may rise up and over the barrier, thus limiting the truck""s resistance to movement away from the dock face. If the barrier does not descend when the weight of the truck forces the ICC bar down, the immoveable barrier might bend the bar under the truck""s added weight.
To allow for incidental vertical movement of a truck""s ICC bar, many vehicle restraints employ pneumatic cylinders for moving the barrier. The compressibility of the air within the cylinder provides a gas spring effect that allows some movement of the barrier even when control valves of the pneumatic system trap the air within the cylinder. In some cases, however, there may be an advantage to using a motor-driven actuator or hydraulics, rather than pneumatics, for moving the barrier. For example, a hydraulically actuated vehicle restraint and a nearby hydraulically actuated dock leveler could perhaps share the same hydraulic pump, tank, and other hydraulic components. Sometimes, hydraulics is preferred over pneumatics to provide a more controlled rate of movement or to positively maintain the position of certain parts after the parts have stopped moving. Moreover, for a pneumatic system, a source of compressed air must be present.
Unfortunately, in applications where a motor-driven actuator or hydraulics is preferred, it can be difficult to provide a vehicle restraint that can allow for vertical movement of the ICC bar once the restraint""s actuator has moved the barrier into position. Further, it can be difficult to provide a restraint that allows for vertical movement of an ICC bar without sacrificing other features of the restraint, such as a low vertical profile when in a lowered, stored position; minimal mechanical complexity; and a switch that ensures that an ICC bar is in position.
In order to provide a low-profile vehicle restraint, the restraint disclosed herein includes a vertically moveable barrier that is moved by an angled actuator from a lowered, stored position to a raised, operative position to obstruct an ICC bar, wherein the restraint allows for incidental vertical movement of the ICC bar after the barrier is at its raised, operative position.
In some embodiments of the restraint, the use of linkages is minimized to perhaps minimize maintenance and improve the reliability of the restraint.
In some embodiments, the restraint includes a compliant coupling that allows for incidental vertical movement of an ICC bar even when the length of a barrier actuator remains substantially constant.
In some embodiments, the compliant coupling can be disposed at either an upper or lower end of the barrier actuator.
In some embodiments, a piston/cylinder or a motor-driven actuator can move the barrier.
In some embodiments of the restraint, the force to vertically move the barrier is transmitted along a generally straight line between the barrier and a frame of the restraint to help provide a strong, reliable barrier/frame connection, and the line of force is inclined to reduce the vertical profile of the restraint when in its lowered, stored position.
In some embodiments, to reduce the vertical profile of the restraint when in its lowered, stored position, the actuator pivots as the barrier moves vertically.
In some embodiments, a pressure relief valve is used to allow for incidental vertical movement of an ICC bar.
In some embodiments, an accumulator is used to allow for incidental vertical movement of an ICC bar.
In some embodiments, the barrier is powered both up and down, rather than relying on spring force, horizontal movement of the truck, the weight of the barrier, or the weight of a trolley that carries the barrier to cause vertical movement.
In some embodiments, a vehicle restraint is provided with an ICC bar sensor that includes a switch actuator captured within the geometry of the restraint""s hook to help protect the switch actuator from damage.